The present disclosure relates generally to a vacuum formed knit sole system for an article of footwear incorporating a knitted component. The present disclosure also relates to an article of footwear comprising the knitted component forming the knit sole system. The present disclosure further is related generally to a method of vacuum forming the knitted component using an insert member to form the knit sole system.
Conventional articles of footwear generally include two primary elements, an upper and a sole structure. The upper is secured to the sole structure and forms a void on the interior of the footwear for comfortably and securely receiving a foot. The sole structure is secured to a lower area of the upper, thereby being positioned between the upper and the ground. In athletic footwear, for example, the sole structure may include a midsole and an outsole. The midsole often includes a polymer foam material that attenuates ground reaction forces to lessen stresses upon the foot and leg during walking, running, and other ambulatory activities. Additionally, the midsole may include fluid-filled chambers, plates, moderators, or other elements that further attenuate forces, enhance stability, or influence the motions of the foot. The outsole is secured to a lower surface of the midsole and provides a ground-engaging portion of the sole structure formed from a durable and wear-resistant material, such as rubber. The sole structure may also include a sockliner positioned within the void and proximal a lower surface of the foot to enhance footwear comfort.
The upper generally extends over the instep and toe areas of the foot, along the medial and lateral sides of the foot, under the foot, and around the heel area of the foot. In some articles of footwear, such as basketball footwear and boots, the upper may extend upward and around the ankle to provide support or protection for the ankle. Access to the void on the interior of the upper is generally provided by an ankle opening in a heel region of the footwear. A lacing system is often incorporated into the upper to adjust the fit of the upper, thereby permitting entry and removal of the foot from the void within the upper. The lacing system also permits the wearer to modify certain dimensions of the upper, particularly girth, to accommodate feet with varying dimensions. In addition, the upper may include a tongue that extends under the lacing system to enhance adjustability of the footwear, and the upper may incorporate a heel counter to limit movement of the heel.
Articles of footwear often are constructed of many components. For example, an article of footwear may include many components, such as an upper, a sockliner, a strobel, a midsole, and an outsole. An outsole may have spikes, cleats, or other protrusions to provide additional traction under selected circumstances. Each of these components is attached to at least one, typically two, and maybe three or more of the other components. Some components thus are stitched to, adhered to, or otherwise attached to other components.
Construction of an article of footwear comprising many components may require that components having significantly different properties and characteristics must be attached to each other. For example, an upper may be formed from cloth, a midsole from soft foam, and an outsole from wear-resistant rubber. These components often can be adhered with adhesives. Adhesive may fail, causing delamination of the components. Further, wear may occur at joints between harder and softer materials, or between dissimilar materials. Therefore, such joints may cause premature failure of the article of footwear. Such joints also may provide uncomfortable sudden transitions between areas of softer or more compliant materials and areas of harder or more rigid materials.
Further, assembly of multiple components may be time-consuming and may lead to errors. For example, components from one style of an article of footwear may incorrectly be used on a different style of footwear. The number of potential errors and premature failures may be significant.
A variety of material elements (e.g., textiles, polymer foam, polymer sheets, leather, synthetic leather) are conventionally utilized in manufacturing an article of footwear. In athletic footwear, for example, the upper may have multiple layers that each include a variety of joined material elements. As examples, the material elements may be selected to impart stretch-resistance, wear-resistance, flexibility, air-permeability, compressibility, comfort, and moisture-wicking to different areas of the upper. Similarly, the sole structure may utilize a number of components to provide selected properties and characteristics. To impart the different properties to different areas of the article of footwear, material elements are often cut to desired shapes and then joined together, usually with stitching or adhesive bonding. Moreover, the material elements often are joined in a layered configuration to impart multiple properties to the same areas. As the number and type of material elements incorporated into the article of footwear increases, the time and expense associated with transporting, stocking, cutting, and joining the material elements also may increase. Waste material from cutting and stitching processes also accumulates to a greater degree as the number and type of material elements incorporated into the article of footwear increases. Moreover, articles of footwear with a greater number of material elements may be more difficult to recycle than articles of footwear formed from fewer types and numbers of material elements. By decreasing the number of material elements utilized in the article of footwear, therefore, waste may be decreased while increasing the manufacturing efficiency and recyclability of the upper.
Reducing the number of material elements may require that one material element provide multiple and additional properties and characteristics sought by users. Thus, there exists a need in the art for articles of footwear comprising a minimum number of material elements while providing a number of properties and characteristics sought by users.